Electrical cable and method of manufacture thereof



Dec. 15, 1931.

ELECTRICAL CABLE AND METHOD OF MANUFACTURE THEREOF Filed July ll, 1925 W. E. BOYLE M336 5?@ I Patented Dec. l5, I19.31

UNITED STATES PATENT `oFF-ici:

` WILLIAMiiiiiovmigornnwYoiiminr.,assmrrommi111mm:Assiermilill'ill,'ro.

ooaroiwrioiv, or Nrw Yonx. I. Y., a coaroiwriorr or m GENERAL CABLE JERSEY Enmarcar. cuni um muon oir maman 'rimamr Application lied July 11, 1985. lerlal In. 48,031.

The present invention relates to paper insulated cable particularly underground and to the manufacture thereof, the o ject of the invention being to produce a cable which will I be more satisfactory in operation than cables now available.

In the distribution of electrical energy it is customary, under certain circumstances, to provide cables which ma be laid underll ground and obviously suc cables must be well insulated and protected to avoid the loss of Yelectrical ener in transmission. The problem of insulating such cablessatisfactorily is anexceedin ly dillicult one,- particu-- ll larly where it is asired to use alternating currents of high voltage as is usually the case because the transmission of Venergy in this manner is the most economical.

The of cable most widely used at the I present time consists essentially of a stranded copper conductor tightly wound with a number of layers of aper impregnated with a suitable compound and covered with a lead sheath. The method of manufacture most l generally employed consists essentially in y wrapping the conductor with the successive layers of paper, placing the cable thus formed in a vacuum considerable length of time, impregnating i l the cable with an oil base compound and then conducting the same to'a lead press for the purpose of applying the lead sheath. Th size of the conductor and thickness of insu# lation d epend of course u on the use for,

which the cable is design and the recise method of manufacture varies with different Y manufacturing concerns.' The paper is usually applied helicall with normal lay and one layer at 'a time, ere bein in the usual cabling machine a number of 'ers or spools ofpaper tape mounted to revolve about the* axis-of the conductor as the'same is moved slowly forward. Paper made :f1-om manila v rope or wood pulp stock is usually employed l and is of a thickness of about ,004 .to .009 of times referred to as condenserpaper, havisess chamber and, after a an inch (4 to 9 mils) the requisite number of layers bein built up asV above indicated.

It would desirable to use a greater number of layers of thinner andA dense'i` paper but the diiculty of applying such a paper with its relatively low tensile strength has liere-v tofore prevented its use. In accordance with the present invention I pro to use a paper of pure linen rag stock suc as is now someing a thickness of a proximately .0005 of an inch (one half 'mil and to provide a construction and method of procedure whereby this character' of paper may be successfully incorporated in the insulation of the cabl The use of a ulplurality of la ers of thin paper is partie arly desirable ause several layers placed together and having the same total'thickness as arsingle layer, posfar greater insulating properties and greater exibility. Instantaneous voltage reak-down tests which I have conducted show that the dielectric strength of an oil impregnated piece-of paper 4 mils in thickness is approximatel 627 volts 'per mil, whereas the same thi ess of paper built u with several lamin of the above lmentioiie thin paper using the vsaine oil for impregnation 'ves a dielectric of approximate y 3000 voltsper mil underthesame 7 5 conditions. t

In'tlie accompanying drawings illustrative 'of the invention, Figure 1 is a plan view of a cable embodying-the present invention and Figures 2 to7 inclusive are cross sections ofinsulating tape which will be later described.

Assuming that it -is dered to follow the present standard practice in respect to the'impregnation of the cable after it has been formed, my invention contemplates the use of alaminated tape, that is a tape having several layers of a'. r, in place of the single thickness tape is now used. For ex' ample, I may use theabove mentioned linen rag stock paper of one-half mil thickness 0 and bring together live thicknesses of said paper and apply the same in the usual man neras a single strip or tape. The laminated tape may be conveniently formed by folding the paperupon itself or by bringing together the requisite number of independent strips.

In order to increase the tensile strength of Y the laminated strip so that it may `withstand the strains incidentyto its applicationfto the conductor and for the further purpose of .giving the strip additional tensile strength to resist bending'strainsV in the cable during its manufacture and installation, I may enclose the layers of very thin paper within an envelope of a stronger paper such as a` manila rope stock paper or kraft papervorany other paper possessing high mechanical lstrength of approximately .O02 of an inch (2 mils) aey in thickness'thus providingav strip of approximately .0065 ofv an inch (G1/2^ mils). be-

'p foreimpregnation for handling in a cabling machine.

fReferring to the accompanying drawings and particularly to Figure 1, a conductor-10 shown surrounded by wrappedv insulation -f11`and enclosed in a lead sheath 12. As will be' readily understood, the insulation 11 Yis built up bysuccessive wrappings .or vlayers of paper. tapev and, in the present instance, the

tape 13 comprises five layers 14 of thin linen rag stock paper of one-half mil thickness whichl are brought together as above described and applied to the cable as a single s strip ortape. A cross section of this tape 1s shown in Figure 2.

' Another tape 15 is shown as comprising i a laminated tape for application to the cable,

and. Figure 5 is a cross section of such a laminated tape enclosed within an envelope 19 of stronger and thicker paper as above described.

Suitable folding apparatus may be used to form the laminatedlstrip and its envelope 0r a broad strip of the linen paper may be ,AIn whicheverv vway the tape lis formed it formed into aV multiwall tube, coveredlwith' a single wall tube of the thicker paper as shown in Figure v6,'wherein 20 designates the p thm paper and 21 the thicker paper and form the tape, 'as shown in Fig-- lattened to ure 7..

maybe suppliedon spools in the usual way Ito the cabling machine and there placed in posltion -upontheconductor afterwhich the C5,

paper covered conductor may be subjected A cross section of this to the. usual vacuum drying and impregna tion steps.

It is further contemplated, however, that the paper may be wholly or partly impregnated prior to its application tothe cable and in that'event the paper in laminated strip form or in the tube formas the case may be, may be led over suitable guides to a drying oven which shouldbe maintained at a temperature of approximately 106 C., and the-apparatus so arranged that the paper remains in this oven for approximately 30 minutes to three hours or until all moisture is dried out. Then, without contact with the air, the paper may be fed to an impregnating oil of petroleum base such as is now commonly used in American practice.V This oil should be maintained at a temperature of approximately 116 C. When sutlicient time has elapsed for the paper to become thorough- 'ly 'impregnated with this oil it may be led to a second bath of similar oil maintainedat a lower temperature of approximately 50 C., and from that bath the paper may be led to and subjected to the action of squeegee rolls or some equivalent device to firmly unite the layers of paper to each other and exclude air therefrom. A

' In the event that the paper is thus wholly or partly impregnated prior to its application to the conductor the nished cable may be subjected to the usual drying and'impregnating processes or inthe course of manufacture subjected to a hot oil bath between the successive applications of the several layers vof laminated tape.

In any. event, after assembly of the conductor and insulation and the impregnation thereof the lead sheathor` other flexible me-` chanical protection may be applied.

A cable constructed as above described will Y structed in accordance with the present invention will be more eiiicient and durable in operation.

The invention may be variously modified and embodied within the scope of the subjoined claims.

' I claim as my ,inventionp 1. A cable for the distribution of electrical energy at high voltages comprising, in combmat1on, a; stranded conductor, an outer moisvture proof sheath, and an intermediate body of. insulatingmaterial including a plurality of layers of paper tape vcomposed of -a plurality of layers of dense paper not exceeding one-half mil in thickness assembled in faceto-face relationship.

2. A cable for the distribution of electrical energy at high voltages, comprising, in combination, a stranded conductor, an outer moisture proof sheath, and an intermediate body of insulating material including a plurality of4 layers of paper tape composed of a plurality of layers of impregnated dense paper approximately one-half mil in thickness assembled in face-to-face relationship.-

3. A cable for the distribution of electrical energy comprising in combination a conductor, an outer moisture proof sheath and an intermediate body of insulating material comprising a plurality of layers of paper tape, each tape being composed of a plurality of layers of relatively thin paper and a surrounding envelope of relatively thick pa er.

4. A cable for the distribution of electrical energy comprising in combination a conductor, an outer moisture proof sheath and an intermediate body of :insulating material comprising a plurality of layers of paper tape, each tape being composed of a plurality of layers of paper of low tensile strength and a-surrounding envelope of paper of higher tensile strength. A

5. A cable for the distribution of electrical energy comprising in combination a conductor, an outer moisture proof sheath and an intermediate body of insulating material comprising a plurality of -layers of paper tape, each tape being composed of a plurality of layers of thin impregnated paper andv a surrounding envelope of thicker and stronger impregnated paper..

an intermediate body of insulating material including a plurality of layers of insulating tape, said tape comprising a plurality of layers of thin, dense paper of low tensile strength and a layer of fibrous material of higher tensile strength assembled in face-toface relationship for unitary application to the cable.

10. A cable for the distribution of electrical energy comprising, in combination, a conductor, ,an outer moisture proof sheath, andl an intermediate-body of insulating material including a plurality of layers of paper tape, said tape comprising a plurality of layers of thin, dense paper and a plurality of layers of relatively thicker paper assembled in face-to-face relationship for unitary application to the cable.

11. A cable for the distribution of electrical energy comprising.I in combination, a conductor, an outer moisture proof sheath, and an intermediate body of insulating material including a plurality of layers of insulating tape', said tape comprising a plurality of layers of thin, dense paper of low. tensile strength and a plurality of layers of fibrous material of higher tensile strength assembled in face-to-face yrelationship' for unitary application to the cable.y

In testimony whereof, I have signed my name to this specification this 10th day of July, 1925.

' WILLIAM BOYLE.

6. A cable for the distribution of electrical f energy comprising in combination a conductor, an outer moisture proof sheath and an intermediate body of insulating material l 8. A cable for the distribution of electrical energyA comprising, in combination, a conductor, an outer moisture proof sheath, and

an intermediate bod'yof insulating material including a plurality of layers of paper tape, said ,tape comprising a plurality of layers of thin, dense paper and a layer of relatively thicker paper assembled in face-to-face relationship for unitary application -to the cable.

9. A cable for the distribution of electrical energy comprising, in combination, a conductor, an outer moisture proof sheath, and 

